These are periods that all teams go through, see Real Madrid, or Barcelona a few years ago.
There are no teams that are free from problems, even Manchester United, who were at the top years ago and are now floating in the middle of the table.
I am sure that Inter will rise from its ashes.
Inter Milan are not mired in problems so they should not be considered a team that is falling even though last season they only finished as runners-up and also did not succeed in the UCL final which caused Inter Milan to miss out on one of the prestigious trophies last season. So in general Inter Milan just need to be better next season because they are a team that has more strength compared to some of the teams you mentioned. While for a team like Manchester United it is fair to say that they have to rise because they finished last season in a bad position.
Your right,every teams has their own Internal problems and Inter Milian is not an exception just like the others but they have to come up with a better strategy that will enable them perform better next season. Imagine Inter Milian not winning a single trophy last season,it's so bad and very annoying for a great team like Inter Milian to perform below expectation and I wouldn't also doubt the fact that PSG were a strong opponent but Inter Milian getting defeated with 5-0 was very disappointing because of the way they were defeated so easily. However we can only hope to see better improvements on the side of inter Milian next season and we can also hope they get it right this time around.